Sympathetic stimulation and arrhythmias

Article Abstract:

The sympathetic nervous system can influence the development of abnormal heart rhythms (arrhythmias) in healthy and in abnormal hearts, whether or not the heart is suffering from a reduced oxygen supply (ischemia). Beta-adrenergic-receptor blockers (drugs that can lower blood pressure and regulate the heartbeat) or heart surgery can prevent these abnormal rhythms, but cause and prevention still remain unclear. In an article in the August 29, 1991 issue of The New England Journal of Medicine, Meredith et al. describes a possible role of the adrenal hormone norepinephrine in the stimulation of the sympathetic nervous system and the subsequent effect on abnormal heart rhythms. However, this hypothesis does not explain why persistent elevation of norepinephrine resulted in only a single episode of abnormal heart rhythms instead of ongoing arrhythmia. This suggests the existence of some other trigger; epinephrine may contribute to this effect or it may be unrelated to the abnormal rhythms. However, evidence indicates that the sympathetic nervous system does play a role, even though the mechanisms remain obscure. The physiological aspects of this and other sources of cardiac stimulation are discussed. (Consumer Summary produced by Reliance Medical Information, Inc.)

Causes of, Physiological aspects, Nervous system, Sympathetic, Sympathetic nervous system, Ventricular tachycardia, editorial

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A comparison of antiarrhythmic-drug therapy with implantable defibrillators in patients resuscitated from near-fatal ventricular arrhythmias

Article Abstract:

The implantable cardiac defibrillator appears to be more effective than antiarrhythmic drugs in reducing the death rate from recurrent arrhythmias in patients with a history of severe arrhythmia. Researchers randomly assigned 1,013 patients who had been resuscitated from ventricular arrhythmias to receive either an implanted defibrillator or an antiarrhythmic drug. Survival rates were higher in the group that received an implanted defibrillator at one, two and three years after treatment. The defibrillator reduced mortality rates by 30% to 40% compared to the drug.

Evaluation, Prevention, Defibrillators, Anti-arrhythmia drugs, Antiarrhythmia agents

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Atrial arrhythmias after cardiothoracic surgery

Article Abstract:

Patients undergoing heart surgery are at risk for arrhythmias of the heart atrium. The exact cause is unknown but inflammation of the heart and imbalance in the autonomic nervous system may be involved. An arrhythmia can lead to blood clot formation and dispersion, which can increase the risk of stroke. Thus these patients should receive anticoagulants as well as drugs to treat the arrhythmia. Beta blockers, digoxin and diltiazem can be considered. Electrical countershock can also be used if the drugs are ineffective. The arrhythmias are usually transient.

Care and treatment, Complications and side effects, Surgery, Postoperative complications, Heart, Heart surgery

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